JEE Chemistry — Electrochemistry
Chemistry questions for JEE Main — Physical, Organic, Inorganic Chemistry.
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Showing 1–10 of 49 questions in Electrochemistry
Q.1 Medium Electrochemistry
A galvanic cell is constructed using Zn|Zn²⁺ and Cu|Cu²⁺ half-cells. If the concentration of Zn²⁺ is increased from 1 M to 10 M at 25°C, how does this affect the cell potential? (E°cell = 1.1 V)
A Decreases by 0.0296 V
B Increases by 0.0296 V
C Increases by 0.059 V
D Remains unchanged
Correct Answer:  A. Decreases by 0.0296 V
EXPLANATION

Using Nernst equation: Ecell = E°cell - (0.059/n)log(Q). Increasing [Zn²⁺] increases Q, making the log term positive, which decreases Ecell. ΔE = -(0.059/2)log(10) = -0.0295 ≈ -0.0296 V.

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Q.2 Medium Electrochemistry
During the electrolysis of molten NaCl using inert electrodes, if 2.3 g of Na is deposited at the cathode, what volume of Cl₂ gas (at STP) will be released at the anode?
A 2.24 L
B 1.12 L
C 4.48 L
D 0.56 L
Correct Answer:  B. 1.12 L
EXPLANATION

At cathode: Na⁺ + e⁻ → Na; moles of Na = 2.3/23 = 0.1 mol. At anode: 2Cl⁻ → Cl₂ + 2e⁻; for 0.1 mol Na, electrons = 0.1 mol, so Cl₂ moles = 0.1/2 = 0.05 mol. Volume at STP = 0.05 × 22.4 = 1.12 L.

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Q.3 Medium Electrochemistry
For the reaction: Fe³⁺ + e⁻ → Fe²⁺ (E° = +0.77 V) and Cl₂ + 2e⁻ → 2Cl⁻ (E° = +1.36 V), which is the strongest oxidizing agent?
A Fe³⁺
B Fe²⁺
C Cl₂
D Cl⁻
Correct Answer:  C. Cl₂
EXPLANATION

The species with highest reduction potential (+1.36 V) is Cl₂, making it the strongest oxidizing agent. Higher E° values indicate greater tendency to accept electrons.

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Q.4 Medium Electrochemistry
The cell potential of a galvanic cell decreases during operation because:
A The concentration of reactants increases
B The concentration of products increases
C Temperature continuously increases
D The electrodes dissolve completely
Correct Answer:  B. The concentration of products increases
EXPLANATION

As the reaction proceeds, product concentrations increase while reactant concentrations decrease, reducing the driving force according to Nernst equation: E = E° - (0.059/n)log(Q).

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Q.5 Medium Electrochemistry
In the electrolysis of dilute H₂SO₄ with inert electrodes, if 2 moles of electrons flow, what volume of gases (in liters at STP) will be produced?
A 11.2 L H₂ and 5.6 L O₂
B 22.4 L H₂ and 11.2 L O₂
C 5.6 L H₂ and 11.2 L O₂
D 5.6 L H₂ and 2.8 L O₂
Correct Answer:  A. 11.2 L H₂ and 5.6 L O₂
EXPLANATION

At cathode: 2H⁺ + 2e⁻ → H₂ (1 mol H₂). At anode: 2H₂O → O₂ + 4H⁺ + 4e⁻ (0.5 mol O₂). With 2 mol e⁻: 1 mol H₂ (11.2 L) and 0.5 mol O₂ (5.6 L).

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Q.6 Medium Electrochemistry
In the electrorefining of copper, impure copper acts as:
A Cathode
B Anode
C Salt bridge
D Electrolyte
Correct Answer:  B. Anode
EXPLANATION

In electrorefining, impure copper acts as anode and undergoes oxidation. Pure copper deposits at cathode. More reactive impurities go into solution.

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Q.7 Medium Electrochemistry
The Gibbs free energy change for an electrochemical cell reaction is related to cell potential by:
A ΔG = nFE
B ΔG° = -nFE°
C ΔG = E/nF
D ΔG° = nFE°
Correct Answer:  B. ΔG° = -nFE°
EXPLANATION

The standard free energy change ΔG° = -nFE°cell, where n is moles of electrons, F is Faraday constant, and E° is standard cell potential.

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Q.8 Medium Electrochemistry
During the electrolysis of aqueous CuSO₄ solution with copper electrodes, which reaction occurs at the cathode?
A SO₄²⁻ → products
B Cu²⁺ + 2e⁻ → Cu
C H₂O → H⁺ + OH⁻
D 2H⁺ + 2e⁻ → H₂
Correct Answer:  B. Cu²⁺ + 2e⁻ → Cu
EXPLANATION

At cathode with copper electrodes in CuSO₄: Cu²⁺ ions are preferentially reduced as their reduction potential (+0.34 V) is higher than H⁺ (-0.83 V).

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Q.9 Medium Electrochemistry
The relationship between equivalent conductance (Λ) and molar conductance (Λm) is:
A Λ = Λm × n
B Λm = Λ × n
C Λ = Λm/n
D Λm = Λ/M
Correct Answer:  A. Λ = Λm × n
EXPLANATION

Λm = κ × 1000/c (molar conductance), Λ = κ × 1000/(c/n) (equivalent conductance). Therefore, Λm = Λ/n or Λ = Λm × n.

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Q.10 Medium Electrochemistry
A current of 5 A is passed through an electrolytic cell for 1930 seconds. Calculate the number of moles of electrons transferred. (Faraday constant = 96500 C/mol)
A 0.1 mol
B 0.5 mol
C 1.0 mol
D 2.0 mol
Correct Answer:  A. 0.1 mol
EXPLANATION

Charge = I × t = 5 × 1930 = 9650 C. Moles of e⁻ = 9650/96500 = 0.1 mol.

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